This invention relates to a method for forming multi-layered metal wiring for a semiconductor element, and more particularly to a method for forming multi-layered metal wiring of aluminum and tungsten, which is suitable to a Damascene structure.
FIGS. 1a-1d show a conventional method for forming multi-layered metal wiring for a semiconductor element.
Referring to FIG. 1a, a lower metal wiring layer 13 is formed by depositing a first insulating layer 12 on a semiconductor substrate 11, and depositing lower metal on the insulating layer 12 and subjecting it to patterning to form a lower metal wiring pattern.
Referring to FIG. 1b, a thick second insulating layer 14 is formed on the first insulating layer 12 having the lower metal wiring pattern 13 formed thereon.
Parts of the second insulating layer 14 are subjected to a photoetching process, and are etched to a predetermined depth using a first photo-mask to form channels for the upper metal wiring pattern to be formed in a subsequent step.
Then, contact portions 15 are formed by etching parts of the second insulating layer 14 to expose the lower metal wiring layer 13. This exposed portion of the lower metal wiring will make contact with the upper metal wiring pattern.
Referring to FIG. 1c, an upper metal layer 16 is deposited on the substrate, filling the channels and the contact portions 15. The upper metal layer 16 is formed of either aluminum deposited by a sputtering method or tungsten deposited by a chemical vapor deposition method.
Referring to FIG. 1d, an upper metal wiring pattern 17 is formed by subjecting the upper metal layer 16 either to an etch back process or to a chemical mechanical polishing process until the second insulating layer 14 is exposed. Thus, conventional multi-layered metal wiring for a semiconductor element can be formed.
The conventional method for forming multi-layered metal wiring for a semiconductor element has provided a Damascene structured upper metal wiring layer formed of a single metal layer of either aluminum or tungsten. When the Damascene structured upper metal wiring pattern is formed of aluminum, the contact opening can be developed, resulting in excess aluminum that can cause shorts.
When the Damascene structured upper metal wiring layer is formed of tungsten, the processing speed of the semiconductor element is reduced due to tungsten's resistance, which is 4 times greater than aluminum.